Layer Stability and Material Properties of Friction-Stir Welded Cu–Nb Nanolamellar Composite Plates

Initial efforts to friction-stir weld (FSW) Cu–Nb nanolamellar composite plates fabricated via accumulative roll bonding are reported in this study. Parent material layers within the composite were nominally 300 nm and exhibited a hardness of 2.5 GPa. After FSW, two types of microstructures were present: a refined layered structure, and an equiaxed nanocrystalline microstructure with grain diameters on the order of 7 nm. The type of microstructure was dependent on location within the FSW nugget and related to varying amounts of strain. Material hardness increased with refinement, with the equiaxed microstructure reaching a maximum hardness of 6.0 GPa.